Farm tractors typically include one or two power take-off shafts extending rearwardly from a vertical wall of the tractor in a position to engage the drive shaft of a trailing implement. Safety shields are typically provided as regular equipment on such tractors to protect the operator from inadvertent contact with a rotating power take-off shaft or the portion of a drive shaft attached to the power take-off shaft.
While such shields serve the intended function, they also make the power take-off shaft or shafts less accessible to the point that they are often considered "in the way" during attachment and detachment of a trailing implement. In the prior art, there have been various attempts to make shields which may be removed or adjusted temporarily to accommodate the attachment and detachment of trailing implements. Among such shields of the prior art are those disclosed in the following U.S. patents:
U.S. Pat. No. 4,553,950 (Teich) PA1 U.S. Pat. No. 4,442,742 (Hartman) PA1 U.S. Pat. No. Re. 30,152 (Davis) PA1 U.S. Pat. No. 3,733,854 (Young et al.) PA1 U.S. Pat. No. 3,504,508 (Bornzin) PA1 U.S. Pat. No. 3,389,763 (Meinert) PA1 U.S. Pat. No. 2,967,432 (Du Shane et al.) PA1 U.S. Pat. No. 2,858,680 (Harrington) PA1 U.S. Pat. No. 2,696,089 (Heth) PA1 U.S. Pat. No. 2,618,980 (Cook) PA1 U.S. Pat. No. 2,410,503 (Johnson) PA1 U.S. Pat. No. 2,443,035 (Hardy)
A number of problems and disadvantages exist with the adjustable power take-off shaft shields of the prior art. There is a tendency for operators, with many such shields, to either remove them permanently because they are considered "in the way" or to leave them adjusted to a position which is not fully protective. Unless such shields are properly returned to their protective positions, they fail, of course, to serve their intended purposes.
However, with many shields of the prior art, adjustment may be somewhat inconvenient, in some cases requiring tools which may not be at hand. Although adjustment may not be very difficult, it is easy to defer or ignore. In some cases, the adjustment of such shields may not be particularly easy to understand.
Certain power take-off shaft shields of the prior art are limited in their adjustability and in some cases get in the way of implement hitches, particularly upper members of the common three-point hitches used on many farm tractors and the like. The shields may be in position to be damaged during hitch operation.
Some other prior power take-off shaft shields are lacking in sturdiness and stability in their protective position(s). Some may tend to bend after a period of use which can cause improper operation such as binding during the movements of adjustment. Some have a top shield member which may tend to rattle excessively during tractor usage.
Power take-off shaft shields are, of course, safety features. If they operate improperly or are considered a nuisance, then they will fail in their primary function. While there have been many improvements and variations, a need for significant improvements in power take-off shaft shields remains.